Integration Issues?

Today I put my (6) 18 week old ee in with my 3 white leghorns (1 roo) and 4 Rhode Island Reds. They are about the same size. As part of the process, I put the small coop right beside the adult's run. They have been there for a couple months (see but no touch). I put some scratch treats and hay into the run prior to integration. My roo was awful. I took him out and put him into the little coop by himself because he was just downright being nasty. My hens are not behaving much better, but really only attack when one gets close to them. I am questioning if I made the transition correctly. I read hiding places? Maybe a board leaned up against the run fence? Ahh I don't know if I made the right decision.

When you wait til they’re that old the other chickens see them as competition.
A lot of people will tell you not to integrate until the younger ones are the same size but it can backfire.
When you integrate younger birds that are still a lot smaller they don’t see them as serious competition for resources.
There’s always going to be pecking and some chasing. You have to let them work it out.
Serious bullying will involve shedding blood.
If there’s no significant wounds then you shouldn’t have to intervene other than providing multiple hiding spots and multiple water/feeders.
It’s all about resources.
Food, water, treats, etc.
Yes hiding places are very helpful.
A board leaning against a wall or fence is a good one.
Also you want multiple food & water stations placed some distance from each other.
That way the older birds can’t guard all of them.

Thank you. I have not seen blood yet, so I guess that's good. I will put more food/water out and have since leaned a piece of plywood inside the run and will probably add more. I will be expanding the run as soon as the fencing arrives (Tues). My current run is about 15X9 and will be putting another roughly 7X5 on the other side of the coop.

Do you free range?
the going consensus seems to be a minimum of 4 square feet per bird in the coop and 10 square feet per bird in the run.
You should have just enough space.
I wouldn’t add any more birds without expanding the coop itself.
Also, when integrating new birds having extra space is going to help.
Another consideration is roost space.
You want about 12” of roost space per bird.
So you’re going to want more than 13 feet of roost for them.
It doesn’t have to all be on one roost.
You could have 3 five foot roosts at different heights.
The lower ranking birds are going to want to be able to roost away from the dominant ones.
They will peck them!
Usually the more dominant birds will use the higher roosts and the lower ranking ones are closer to the ground.
Just today we added extra roosts to our coop to make it easier for our bantams to get away from the bigger birds.
For some reason when they all go to bed can be the most stressful time until it gets dark and they settle down.